It is known to integrate in separate surface areas of a common semiconductive chip both an insulated gate field effect transistor and a bipolar transistor. However, the need for separate surface areas for the two transistors limits the packing density possible.
It has also been proposed hitherto to use common or over surface areas of a semiconductive chip to form various composite devices, particularly for use in power applications, such as variants of silicon controlled rectifiers, but these devices are not particularly suited for use as components of a logic circuit, where small size, high density and fast switching speeds are particularly important.